Polymerizable, chiral compounds and their use

ABSTRACT

The invention relates to chiral compounds containing at least one divalent or polyvalent chiral group, at least one polymerizable group, at least one spacer and at least one mesogenic group, and to their use as polymerizable, chiral dopes for the preparation of cholesteric networks. The novel compounds are suitable for use in electro-optical displays or as chiral dopes for nematic or cholesteric liquid crystals in order to produce layers which reflect in colors.

This application is a 371 of PCT/EP94/04055 filed Dec. 6, 1994.

It is known that molecules which are anisotropic in shape can formliquid-crystalline phases, known as mesophases, on warming. Theindividual phases differ through the spatial arrangement of the majorparts of the molecules on the one hand and through the moleculararrangement with respect to the long axes on the other hand (G. W. Gray,P. A. Winsor, Liquid Crystals and Plastic Crystals, Ellis HorwoodLimited, Chichester, 1974). The nematic liquid-crystalline phase isdistinguished by the fact that there is only one alignment long-distanceordering due to the long molecular axes lining up in parallel. Under theprerequisite that the molecules making up the nematic phase are chiral,a cholesteric phase forms, in which the long axes of the molecules forma helical superstructure perpendicular thereto (H. Baessler,Festkorperprobleme XI, 1971). The chiral moiety may be present in theliquid-crystalline molecule itself or added to the nematic phase as adope. Phases produced by doping are known as induced cholesteric phases.This phenomenon was first studied on cholesterol derivatives (H.Baessler, M. M. Labes, J. Chem. Phys. 52 (1970) 631; H. Baessler, T. M.Laronge, M. M. Labes. J. Chem. Phys. 51 (1969) 3213; H. Finkelmann, H.Stegemeyer, Z. Naturforschg. 28a (1973) 799). The induction ofcholesteric phases later also became possible through addition of otherchiral substances which themselves are not liquid-crystalline (H.Stegemeyer, K. J. Mainusch, Naturwiss. 58 (1971) 599; H. Finkelmann, H.Stegemeyer, Ber. Bunsenges. Phys. Chem. 78 (1974) 869).

The cholesteric phase has remarkable optical properties: large opticalrotation and pronounced circular dichroism caused by selectivereflection of circular-polarized light within the cholesteric layer. Thedifferent colors to be observed depending on the viewing angle depend onthe pitch of the helical superstructure, which is itself dependent onthe twisting power of the chiral component. The pitch and thus thewavelength range of the selectively reflected light of a cholestericlayer can be varied, in particular, by changing the concentration of achiral dope (J. E. Adams, W. E. L. Haas, Mol. Cryst. Liq. Cryst. 16(1972) 33). Such cholesteric systems offer interesting opportunities forpractical use. Thus, incorporation of chiral moieties into mesogenicacrylic esters after alignment in the cholesteric phase andphotocrosslinking can give a stable, colored network, but theconcentration of the chiral component therein cannot be changed (G.Galli, M. Laus, A. Angeloni, Makromol. Chem. 187 (1986) 289).Furthermore, admixing of non-crosslinkable, chiral compounds withnematic acrylic esters after photocrosslinking can give a coloredpolymer (I. Heynderickx, D. J. Broer, Mol. Cryst. Liq. Cryst. 203 (1991)113), but this still contains volatile constituents which prevent use.

It is an object of the present invention to provide novel chiralcompounds which firstly have a high twisting power and secondly can beincorporated in a stable manner into the cholesteric phase in anydesired concentration without diffusing out of the phase orcrystallizing.

We have found that this object is achieved by polymerizable, chiralcompounds.

The present invention accordingly provides polymerizable, chiralcompounds containing at least one divalent or polyvalent chiral group,at least one polymerizable group, at least one spacer and at least onemesogenic group, and to their use as polymerizable, chiral dopes for thepreparation of cholesteric networks.

The polymerizable groups here are, in particular, vinyl radicals, whichare present, for example, in acrylic compounds, vinyl ethers or styrenederivatives. Epoxides are also suitable.

Chiral groups which are suitable for the novel compounds are derived, inparticular, from sugars, bifunctional or polyfunctional compounds fromthe biphenyl or binaphthyl series, optically active glycols, dialcoholsor amino acids.

The spacers and mesogenic groups are the radicals conventionally usedfor this purpose.

The groups necessary for the novel compounds are linked to one anothervia bridges, such as O, COO, OCO, CONH, NHCO, CON(R), N(R)CO or a directbond.

In particular, the present invention provides compounds of the formula I

    (Z-Y-A-Y-M-Y-).sub.n X I,

where, in each case independently of one another,

A is a spacer,

M is a mesogenic group,

Y is a direct bond O, S, COO, OCO, CON(R) or N(R)CO,

Z is a polymerizable group,

n is a number from 2 to 6,

X is a chiral radical and

R is C₁ - to C₄ -alkyl or hydrogen.

The spacers A can be any groups known for this purpose; the spacers areusually linked to X via ester or ether groups or a direct bond. Thespacers generally contain from 2 to 30, preferably from 2 to 12, carbonatoms and may be interrupted in the chain, for example by O, S, NH orNCH₃. Possible substituents for the spacer chain are fluorine, chlorine,bromine, cyano, methyl or ethyl.

Examples of representative spacers are: ##STR1## where

m is from 1 to 3 and

p is from 1 to 12.

The radicals M can again be the known mesogenic groups. Particularlysuitable are radicals containing cycloaliphatic, aromatic orheteroaromatic groups. The mesogenic radicals conform, in particular, tothe formula II

    (-T-Y.sup.1).sub.r -T                                      II

where

each T, independently of the others, is cycloalkylene, an aromaticradical or a heteroaromatic radical,

each Y¹, independently of the others, is O, COO, OCO, CH₂ O, OCH₂, CH═N,N═CH or a direct bond, and

r is from 0 to 3.

r is preferably. 0 or 1.

T is generally a non-aromatic or aromatic, carbocyclic or heterocyclicring system, which is unsubstituted or substituted by fluorine,chlorine, bromine, cyano, hydroxyl or nitro, and which conforms, forexample, to one of the following basic structures: ##STR2##

Particularly preferred mesogenic groups M are, for example: ##STR3## nin the formula I is preferably 2 or 3, in particular 2.

of the chiral radicals X, availability means that particular preferenceis given to those derived from sugars, binaphthyl or biphenylderivatives or optically active glycols or dialcohols. In the case ofsugars, particular mention may be made of pentoses and hexoses, andderivatives thereof.

Examples of individual radicals X are: ##STR4## where L is C₁ - to C₄-alkyl, C₁ -C₄ -alkoxy, halogen, COOR, OCOR, CONHR or NHCOR, where R isas defined above.

Particular preference is given to, for example, ##STR5##

Optically active glycols or derivatives thereof correspond, .forexample, to the formula ##STR6## where B¹ und B², independently of oneanother, are C₁ to C₄ -alkyl, which may be substituted by hydroxyl andinterrupted by --O--, or are phenyl or substituted or unsubstitutedcarboxyl, and one of the radicals is alternatively hydrogen, where, inthe case of identical radicals B¹ and B², the configuration R,S isexcluded.

Individual such radicals B¹ and B² are, for example,

CO₂ CH₃, CO₂ CH₂ CH₃, CO₂ (CH₂)₂ CH₃, CO₂ (CH₂)₃ CH₃, CO₂ CH(CH₃)₂, CO₂C(CH₃)₃ or --CH(OH)CH₂ (OH).

Also suitable are specific bifunctional chiral groups which have thefollowing structures: ##STR7##

Examples of preferred radicals Z are: ##STR8##

where R is as defined above.

The units Z-Y-A-Y-M-Y according to the invention, where Z, Y, A and Mare as defined above, can be obtained by synthetic methods which areknown in general terms, as described, for example, in DE-A 39 17 196.

The chiral moieties can be obtained commercially and are thus available.

The novel compounds are particularly suitable for use in electro-opticaldisplay elements or as chiral dopes for nematic or cholesteric liquidcrystals in order to produce layers which reflect in colors.

EXAMPLE 1

2,5-Bis4'-(2-acryloyloxyethoxy)biphenyl-4-carbonyloyl!-1,4;3,6-dianhydro-D-sorbitol##STR9## a Ethyl 4'-hydroxyethoxybiphenyl-4-carboxylate ##STR10##

72.6 g (0.3 mol) of ethyl 4'-hydroxybiphenyl-4-carboxylate are dissolvedin 225 ml of absolute dimethylformamide, and 45.5 g (0.33 mol) ofpotassium carbonate and 3.0 of potassium iodide are added. 26.57 g (0.33mol) of 2-chloroethanol are then added, and the mixture is heated at100° C. for 5 hours. After the mixture has been stirred overnight atroom temperatures a further 22.77 g (0.17 mol) of potassium carbonateand 13.3 g (0.17 mol) of

2-chloroethanol are added. The mixture is heated at 100° C. for afurther 15 hours, cooled and precipitated in water. The solid residue iswashed with water to neutral and dried. The moist product canimmediately be reacted further.

Yield: 123 g of moist product, m.p. (pure substance) 128°-129° C.

b 4'-Hydroxyethoxybiphenyl-4-carboxylic acid ##STR11##

123 g (about 0.3 mol) of water-moist ethyl4'-hydroxyethoxybiphenyl-4-carboxylate are dissolved in 258 ml ofethanol, and 67.22 g (0.6 mol) of 50% strength KOH solution are added.The mixture is refluxed for one hour and cooled, and the residue isfiltered off, washed with ethanol and sucked dry. The crude product isstirred in water and acidified with dilute hydrochloric acid. After themixture has been stirred for a number of hours, the product is filteredoff with suction, washed with water to neutral and dried.

Yield: 68.0 g=88%, m.p. 155° C.

c 4'-(2-Acryloyloxyethoxy)biphenyl-4-carboxylic acid ##STR12##

38.7 g (0.15 mol) of 4'-hydroxyethoxybiphenyl-4-carboxylic acid aredissolved in 220 ml of 1,1,1-trichloroethane, and 54.0 g (0.75 mol) offreshly distilled acrylic acid and 0.5 g of hydroquinone are added. 10.0g of p-toluenesulfonic acid are added, and the mixture is refluxed on awater separator for 4 hours. A further 54.0 g (0.75 mol) of distilledacrylic acid are then added, and the mixture is heated for a further 3.5hours until everything is dissolved. The mixture is cooled, the residueis filtered off with suction, washed with 1,1,1-trichloroethane andsubsequently stirred with t-butyl methyl ether and water. The solidresidue is filtered off with suctions washed with t-butyl methyl ether,dried and recrystallized from 1.4 l of ethyl acetate.

Yield: 19.0 g =41%.

d 2-(4'-Chlorocarbonylbiphenyl-4-yloxy)ethyl acrylate ##STR13##

9.36 g (0.03 mol) of 4'-(2-acryloyloxyethoxy)biphenyl-4-carboxylic acidare introduced into 25 ml of oxalyl chloride, and one drop ofdimethylformamide is added. A spatula tip of 2,6-di-t-butylmethylphenolis added as free-radical inhibitor, and the reaction mixture is thenheated at 40°-50° C. for 35 minutes. The excess oxalyl chloride issubsequently removed by distillation in a water-pump vacuum, and theoily residue which remains is dried overnight in an oil-pump vacuum. Theproduct can be processed further directly.

Yield: 10.1 g =99%.

e 2,5-Bis4'-(2-acryloyloxyethoxy)biphenyl-4-carbonyloyl!-1,4;3,6-dianhydro-D-sorbitol

1.99 g (0.014 mol) of 1,4;3,6-dianhydro-D-sorbitol are dissolved in 50ml of absolute dichloromethane, and 2.37 g (0.03 mol) of absolutepyridine and a spatula tip of 2,6-di-t-butylmethylphenol are then added,and subsequently 9.93 g (0.03 mol) of2-(4'-chlorocarbonylbiphenyl-4-yloxy)ethyl acrylate dissolved in 20 mlof absolute dichloromethane are added dropwise at 0°-5° C. The mixtureis stirred overnight with slow warming, water and a little dilutehydrochloric acid are then added, and the mixture is extracted a numberof times with ether. The combined organic phases are washed with water,dried using Na₂ SO₄ and freed from solvent. The product is purified bycolumn chromatography (silica gel, eluent: toluene/ethyl acetate 8:2).

Yield: 0.91 g =9%, m.p.>175° C.

¹ H-NMR (200 MHz, CDCl₃):

δ=4.11 (d, J=6.3 Hz, 2H, --CH₂ --, ring H), 4.15 (m, 2H, --CH₂ --, ringH), 4.25 (t, J=6 Hz, 4H, --CH₂ --OAr), 4.55 (t, J=6 Hz, 4H, --CH₂--OCOR), 4.75 (d, J=6 Hz, 1H, bridge H). 5.13 (t, J=6 Hz, 1H, bridge H),5.45 (q, J=6 Hz, 1H, ring H), 5.55 (m, 1H, ring H), 5.88 (d, J=10.6 Hz,2H, olef. H), 6.20 (dd, J=17 Hz, J'=10.6 Hz, 2H, olef. H), 7.0 (d, J=8.6Hz, 4H, arom. H), 7.5-7.7 (m, 8H, arom. H), 8.06 (d, J=8.6 Hz, 2H, arom.H), 8.13 d, J=8.6 Hz, 2H, arom. H).

EXAMPLE 2

2,5-Bis4'-(2-acryloyloxyethoxy)phenyl-4-carbonyloyl!-1,4;3,6-dianhydro-D-sorbitol##STR14##

The compound was prepared by a method similar to that of Example 1 usingethyl 4-hydroxybenzoate.

Yield: 1.24 g =16%, m.p. >156° C.

¹ H-NMR (200 MHz, CDCl₃):

δ=4.05 (d, J=5.7 Hz, 2H, --CH₂ --, ring H ), 4.12 (m, 2H, --CH₂ --, ringH), 4.24 (t, J=6 Hz, 4H, --CH₂ --OAr), 4.56 (t, J=6 Hz, 4H, --CH₂--OCOR), 4.70 (d, J=6 Hz, 1H, bridge H), 5.08 (t, J=6 Hz, 1H, bridge H),5.40 (q, J=6 Hz, 1H, ring H), 5.46 (m, 1H, ring H), 5.82 (d, J=10.7 Hz,2H, olef. H), 6.18 (dd, J=17 Hz, J'=10.7 Hz, 2H, olef. H), 6.48 (d, J=17Hz, 2H, olef. H), 6.95 (d, J=8.3 Hz, 2H, arom. H), 7.0 (d, J=8.3 Hz, 2H,arom. H), 7.95 (d, J=8.3 Hz, 2H, arom. H), 8.05 (d, J=8.3 Hz, 2H, arom.H).

EXAMPLE 3

2,5-Bis4'-(2-acryloyloxyethoxy)biphenyl-4-carbonyloyl!-1,4;3,6-dianhydro-D-mannitol##STR15##

The compound was prepared by a method similar to that of Example 1 using1,4;3,6-dianhydro-D-mannitol.

Yield: 1.18 g =12%, m.p.>195° C.

¹ H-NMR (200 MHz, CDCl₃):

δ=3.82 (dd, J=6.3 Hz, J'=3 Hz, 2H, --CH₂ --, ring H), 3.88 (dd, J=6.3Hz, J'=3 Hz, 2H, --CH₂ --, ring H), 4.15 (t, J=6 Hz, 4H, --CH₂ --OAr),4.4 (t, J=6 Hz, 4H, --CH₂ --OCOR), 4.8 (m, 2H, bridge H), 5.25 (m, 1H,bridge H), 5.35 (m, 1H, ring H), 5.85 (d, J=10.4 Hz, 2H, olef. H), 6.15(dd, J=16 Hz, J'=10.4 Hz, 2H, olef. H), 6.4 (d, J=16 Hz, 2H, olef. H),7.1 (d, J=8.5 Hz, 4H, arom. H), 7.55 (d, J=8.5 Hz, 4H, arom. H), 8.0 (d,J=8.5 Hz, 4H, arom. H), 8.1 (d, J=8.5 Hz, 4H, arom. H).

EXAMPLE 4

2,5-Bis4'-(2-acryloyloxyethoxy)biphenyl-4-carbonyloyl!-1,4;3,6-dianhydro-L-iditol##STR16##

The compound was prepared by a method similar to that of Example 1 using1,4;3,6-dianhydro-L-iditol.

Yield: 1.89 g =19%, m.p. >195° C.

¹ H-NMR (200 MHz, CDCl₃):

δ=3.93 (dd, J =11.0 Hz, J'=3.0 Hz, 2H, --CH₂ --, ring H), 3.98 (dd,J=11.0 Hz, J'=3 Hz, 2H, --CH₂ --, ring H), 4.30 (t, J=6 Hz, 4H, --CH₂--OAr), 4.50 (t, J=6 Hz, 4H, --CH₂ --OCOR), 5.35 (s, 2H, bridge H), 5.65(dd, J=11.0 Hz, J'=3 Hz, 2H, bridge H), 5.90 (d, J=10.7 Hz, 2H, olef.H),6.20 (dd, J=16.0 Hz, J'=10.7 Hz, 2H, olef. H), 6.55 (d, J =16 Hz, 2H,olef. H), 7.1 (d, J=8.7 Hz, 4H, arom. H), 7.50 (d, J=8.7 Hz, 4H, arom.H), 8.12 (d, J=8.7 Hz, 4H, arom. H), 8.13 (d, J=8.7 Hz, 4H, arom. H).

EXAMPLE 5

2,5-Bis4'-(2-acryloyloxyethoxy)biphenyl-4-carbonyloyl!-1,4;3,6-dianhydro-L-iditol##STR17##

The compound was prepared by a method similar to that of Example 1 usingdiethyl (R,R)-tartrate.

Yield: 2.22 g =20%, m.p. 146° C.

1H-NMR (200 MHz, CDCl₃):

δ=1.28 (t, J=6.9 Hz, 6H, ester CH₃), 4.15 (q, J=6.9 Hz, 4H, ester CH₂),4.3 (t, J=6.0 Hz, 4H, --CH₂ --O--arom.), 4.55 (t, J=6.0 Hz, 4H, --CH₂--O--COR), 5.88 (d, J=11.3 Hz, 2H, olef. H), 6.04 (s, 2H, --CH(OR)(CO₂R)), 6.16 (dd, J=17.3, J'=11.3 Hz, 2H, olef. H), 6.48 (d, J=17.3 Hz, 1H,olef.H), 7.05 (d, J=8.6 Hz, 4H, arom. H), 7.57 (d, J=8.6 Hz, 4H, arom.H), 7.68 (d, J=7.6 Hz, 4H, arom. H), 8.16 (d, J=7.6 Hz, 4H, arom. H).

The compounds shown in the tables below, which have similar physicalproperties, can also be prepared by methods similar to those described.

                                      TABLE 1                                     __________________________________________________________________________     ##STR18##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________         ##STR19##                                                                8                                                                                  ##STR20##                                                                9                                                                                  ##STR21##                                                                10                                                                                 ##STR22##                                                                11                                                                                 ##STR23##                                                                12                                                                                 ##STR24##                                                                13                                                                                 ##STR25##                                                                14  R.sup.1, R.sup.2 random mixture of the radicals from Examples 7,              10 and 12, employed in the ratio 1:1:1.                                   __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________     ##STR26##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________    15                                                                                 ##STR27##                                                                16                                                                                 ##STR28##                                                                17                                                                                 ##STR29##                                                                18                                                                                 ##STR30##                                                                19                                                                                 ##STR31##                                                                __________________________________________________________________________

                                      TABLE 3                                     __________________________________________________________________________     ##STR32##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________    20                                                                                 ##STR33##                                                                21                                                                                 ##STR34##                                                                22  R.sup.1, R.sup.2 random mixture of the radicals from Examples 9,              11 and 13, employed in the ratio 1:1:1.                                   __________________________________________________________________________

                                      TABLE 4                                     __________________________________________________________________________     ##STR35##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________    23                                                                                 ##STR36##                                                                24                                                                                 ##STR37##                                                                25                                                                                 ##STR38##                                                                26                                                                                 ##STR39##                                                                27                                                                                 ##STR40##                                                                28  R.sup.1, R.sup.2 random mixture of the radicals from Examples 23              and 25, employed in the ratio 2:1.                                        __________________________________________________________________________

                                      TABLE 5                                     __________________________________________________________________________     ##STR41##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________    29                                                                                 ##STR42##                                                                30                                                                                 ##STR43##                                                                31  R.sup.1, R.sup.2, R.sup.3 random mixture of the radicals from                 Examples 7, 10 and 12, employed in the ratio 1:1:1.                       __________________________________________________________________________

                                      TABLE 6                                     __________________________________________________________________________     ##STR44##                                                                    Ex-                                                                           ample                                                                         __________________________________________________________________________    32                                                                                 ##STR45##                                                                33                                                                                 ##STR46##                                                                34                                                                                 ##STR47##                                                                __________________________________________________________________________

                                      TABLE 7                                     __________________________________________________________________________    The compounds can be synthesized by a method similar to that of               Example 2.                                                                     ##STR48##                                                                    __________________________________________________________________________    Example 35       n = 4                                                                             HTP: 41.5 μm.sup.-1                                   Example 36       n = 6                                                                             HTP: 44.7 μm.sup.-1                                   Example 37       n = 8                                                                             HTP: 47.7 μm.sup.-1                                   Example 38       n = 11                                                                            HTP: 52.3 μm.sup.-1                                   __________________________________________________________________________     HTP = helical twisting power                                             

The compounds of Examples 39 to 42 are obtained by a procedure similarto that of Example 2 by reaction with methyl4,6-benzylidene-α-D-glucopyranoside.

                  TABLE 8                                                         ______________________________________                                         ##STR49##                                                                    Exam-                                                                         ple                                                                           ______________________________________                                        39                                                                                     ##STR50##                                                            40                                                                                     ##STR51##                                                            41                                                                                     ##STR52##                                                            42                                                                                     ##STR53##                                                            ______________________________________                                    

The compounds of Examples 43 to 47 are obtained by a method similar tothat of Example 2 by reaction of the chiral radical with4'-(ω-vinyloxy)alkyleneoxyphenyl-4-carboxylic acids.

    ______________________________________                                         ##STR54##                                                                    Exam-                                                                         ple                                                                           ______________________________________                                        43                                                                                       ##STR55##                                                          44                                                                                       ##STR56##                                                          45                                                                                       ##STR57##                                                          46                                                                                       ##STR58##                                                          47                                                                                       ##STR59##                                                          ______________________________________                                    

We claim:
 1. A compound of the formula

    (Z-Y-A-Y-M-Y-).sub.n X                                     I,

where, in each case independently of one another, A is a spacer, M is agroup of the formula (T-Y¹)_(r) -T, Y is a direct bond, O, S, COO, OCO,CON(R) or N(R)CO, Z is a polymerizable group, n is a number from 2 to 6,X is a chiral furan or bi-furan radical, R is C₁ - to C₄ -alkyl orhydrogen, T is cycloalkylene, an aromatic radical or a pyrimidineradical, Y¹ is O, COO, OCO, CH₂ O, OCH₂, CH═N, N═CH or a direct bond,and r is from 0 to
 3. 2. A compound as claimed in claim 1, where r is 0or
 1. 3. A compound as claimed in claim 1, where n=2.
 4. A compound asclaimed in claim 1, where X is ##STR60##
 5. A compound as claimed inclaim 2, where X is ##STR61##
 6. In a process for the preparation of acholesteric network, the improvement comprising incorporating thecompound of claim 1 therein as a polymerizable, chiral dope.
 7. Thepolymerizable, chiral compound as claimed in claim 1, wherein A is achain of 2-30 carbon atoms, optionally interrupted in the chain with O,S, NH or NCH₃, and optionally substituted on the chain with fluorine,chlorine, bromine, cyano, methyl or ethyl;and wherein Z is selected fromthe group consisting of the following structures: ##STR62## where R isdefined above.